I'd go with the Shield. Or even the M&P 9C/40C. They're not a whole lot bigger. Both the Shield & 40C will allow you to purcha & put a 9MM barrel in it. In the 40C you can also put a .357sig barrel in it & even use the same .40 cal mags.
Then there are Glocks... (I'm partial to M&P & Glock)